Reactive Yellow 145 Dye Adsorption from Aqueous Solution Using KOH-Activated Banana Peel Carbon: Isotherm, Kinetics, and Thermodynamic Studies

Abstract

Activated banana peel carbon (BPAC) was prepared and evaluated as an adsorbent for Reactive Yellow 145 (RY 145) dye from aqueous solution. BPAC was prepared from Musa x paradisiaca peels via carbonization at 400 °C followed by KOH activation at 650 °C. Structural analysis affirmed the formation of a highly porous, predominantly amorphous carbon having abundant oxygen-containing functional groups suitable for dye adsorption. Batch adsorption studies established that the efficiency was strongly influenced by solution pH (pH 2), adsorbent dosage (25 mg), contact time (90 min.), and initial dye concentration (200 mg L^-1). The Langmuir isotherm showed better representation of the equilibrium data with R² = 0.976, which was higher than the Freundlich model (R² = 0.923), suggesting monolayer adsorption on a relatively homogeneous surface with a maximum adsorption capacity of 159.0 mg g^-1. Thermodynamic data revealed that the uptake process was spontaneous (ΔG° = −1.187 kJ mol⁻¹ at 323 K), endothermic (ΔH° = 7.211 kJ mol⁻¹), and accompanied by a slight increase in interfacial randomness (ΔS° = 26 J mol⁻¹ K⁻¹). Generally, the BPAC displayed good adsorption performance and represents a promising biomass-derived adsorbent for the treatment of dye-contaminated wastewater.